Direct search for the Higgs boson to charm coupling at ATLAS

A direct search for the Standard Model Higgs boson decays to a pair of charm quarks is presented. This analysis uses the full LHC Run 2 dataset collected with the ATLAS detector, corresponding to an integrated luminosity of 139 inverse femtobarns of proton-proton collisions at a centre-of-mass energy of 13 TeV. An extrapolation of this search to the HL-LHC conditions (centre-of-mass en- ergy of 14 TeV, integrated luminosity of 3000 inverse femtobarns) is also presented. The production of the Higgs boson in association with a W or Z boson decaying leptonically is measured. Flavour jet tagging algorithms are used to identify the signature of the Higgs boson decay to charm quarks, while reducing contamination from Higgs boson decays to bottom quarks. This search improves the constraint on the cross section times branching fraction for a Standard Model Higgs boson previously presented by ATLAS, using an integrated luminosity of 36 inverse fem- tobarns of proton-proton collisions at the same centre-of-mass energy. A constraint on the charm Yukawa coupling modifier from Higgs boson to charm quark decays is also set. The HL-LHC extrapolation of this search further improved the expected constraints.